I have 3 silver arowanas that used to be very jittery when I move, but have calmed down a bit. However, as soon as the lights go off, they seem more afraid than usual. Everytime I walk by them at night they panic to no end until I leave, thrashing around. This scares me because they might be hurting themselves. Is it normal for arowanas to be more panicky at night? And do they ever sleep?